ARM: dts: msm: set APC supply ncp6335d regulator to PWM mode for msm8926

Alternating CPR UP and DOWN interrupts have been observed on MSM8926v2 CDP
boards. This behavior is caused by the interaction of CPR controller
configuration parameters and high voltage ripple on the VDD_APC supply
which is output by an Onsemi NCP6335D regulator operating in AUTO mode.
Change the configuration of the Onsemi regulator so that PWM mode is used
in place of AUTO mode. PWM mode exhibits significantly less ripple than
AUTO mode so the CPR controller does not have a problem with it.

CRs-Fixed: 607899
Change-Id: I48c41fa77d4b092ed6abb433a868e409b578ea7e
Signed-off-by: Ke Liu <keliu@codeaurora.org>